The present invention relates to an AC generator for use in a vehicle which achieves ventilation and cooling by use of fans provided in a bracket support type rotor and, in particular, to the improved cooling of a stator coil.
Referring to FIG. 3 , there is shown a section view of a conventional AC generator for use in a vehicle. In FIG. 3 , a stator 1 comprises a stator iron core 2 and a stator coil 3. A rotor 4 is constructed in the following manner. That is, heteropolar magnetic pole iron cores 5 and 6 are included, in which the respective magnetic pole tooth portions are projected out alternately in the circumferential direction of the rotor 4. An exciting coil 7 is held by and between the magnetic pole iron cores 5 and 6. A rotary shaft 8 is fixedly secured the two magnetic pole iron cores 5 and 6. A pair of slip rings 9 are fixed to the rotary shaft 8 through insulation sleeves, respectively. Fans 10 and 11 are fixed to the magnetic pole iron cores 5 and 6, respectively, and include blades 10a and 11a, respectively.
Next, front and rear brackets 12 and 13 connect the parts of the stator iron core 2 by means of a fastening bolt 14. In the front bracket 12, there is formed a plurality of air suction holes 12a and a plurality of air exhaust holes 12b for ventilation. Also, in the rear bracket 13, similarly, there are formed a plurality of air suction holes 13a and a plurality of air exhaust holes 13b for ventilation. The rotary shaft 8 is supported by the front and rear brackets 12 and 13 through bearings 15 and 16. A pulley 17 is fixed to the rotary shaft 8. When the rotational movements of an engine of a vehicle are transmitted through a belt to the pulley 17, then the pulley 17 allows the rotary shaft 8 to rotate.
Further, a rectifier 18 rectifies an alternating current into a direct current, in which the current is produced by an alternating voltage induced in the stator coil 3. A voltage regulator 19 detects a generator voltage, controls an exciting current, and regulates a terminal voltage to a given value. A brush holder 20 holds and presses a brush 21 against the slip rings 9.
In the above-mentioned conventional AC generator, when the rotor 4 is rotated, an alternating voltage is induced in the stator coil 3, so that electric power is supplied and heat is generated. The ventilative air due to the rotational movements of the fans 10, 11 cools areas of the stator 1 and the rotor 4.
Cooling air caused by the rotation of the fan 10, as shown by an arrow A in FIG. 3 , is sucked in through the air suction holes 12a of the front bracket 12, and is then discharged out through the air exhaust holes 12b of the front bracket 12 so as to cool the area of the stator 1. On the other hand, cooling air caused by the rotation of the fan 11, as shown by an arrow B in FIG. 3, is sucked in through the air suction holes 13a of the rear bracket 13, and is then discharged out through the air exhaust holes 13b of the rear bracket 13 so as to cool the rectifier 18, the voltage regulator 19, the area of electricity collector part, and the area of the stator 1.
In the above-mentioned conventional vehicle AC generator of the above type, the end portion of the stator coil 3 is overlapped only slightly in the axial direction of the stator coil 3 on the blades, 10a and 11a of the fans 10 and 11 and therefore the cooling air generated by the fans 10 and 11 flow past only a portion of the coil end portion, with the result that the stator coil 3 cannot be cooled effectively.